Positive Type Resist Composition, Process for Forming Resist Pattern, and Process for Performing Ion Implantation

ABSTRACT

A positive resist composition which is obtained by dissolving (A) a resin ingredient for resists and (B) an acid generator ingredient in an organic solvent, wherein the ingredient (A) comprises (A1) a resin ingredient for resists which has the structural unit (a1), structural unit (a2), and structural unit (a3) shown below and which comes to have enhanced alkali solubility by the action of an acid. Structural unit (a1): unit represented by the following general formula (1). Structural unit (a2): unit derived from an (α-lower alkyl)acrylic ester having a lactone-containing monocyclic or poly-cyclic group. Structural unit (a3): unit derived from an (α-lower alkyl)acrylic ester having a polyalicyclic hydrocarbon group containing a polar group. (In the formula, represents hydrogen or lower alkyl; and R 11  represents an acid-dissociable dissolution-inhibitive group comprising chain tertiary alkyl.)

TECHNICAL FIELD

The present invention relates to a positive type resist composition, aprocess for forming a resist pattern, and a process for performing ionimplantation.

Priority is claimed on Japanese Patent Application No. 2004-134075,filed Apr. 28, 2004, the content of which is incorporated herein byreference.

BACKGROUND ART

In recent years, in the production of semiconductor devices orliquid-crystal-display elements, down-sizing has rapidly progressed asthe lithographic technology advances. In general, as a method fordown-sizing, wavelength of an exposure light source is shortened.Specifically, KrF excimer laser (248 nm) and ArF excimer laser (193 nm)are introduced now, although the ultraviolet rays represented by g lineor i line were used conventionally.

As a resist for use in such an excimer laser, a chemically amplifiedresist composition which satisfies the conditions for high resolutionwhich can reproduce a fine pattern is known, and the resist consists ofa base resin having alkali solubility which changes by an action ofacid, and an acid generator which generates an acid upon being exposed,as the basic components. The above chemically amplified resistcomposition involves both a negative type which contains an acidgenerator, a cross-linking agent, and an alkali-soluble resin as a baseresin, and a positive type which contains an acid generator and a resinof which alkali solubility increases by the action of acid.

Hitherto, in the KrF excimer laser lithography, as a base resin of achemically amplified resist, polyhydroxy styrene having a hightransparency to a KrF excimer laser (248 nm) and a derivative therefromobtained by protecting its hydroxyl group with an acid-dissociable,dissolution-inhibiting group (protecting group) has been generally used.

Furthermore, down-sizing of semiconductor devices has progressedincreasingly, development of processes using an ArF excimer laser (193nm) has been furthered energetically, and resists for use in ArF havingvarious compositions have been proposed. Among them, an acrylic typeresin with a high transparency at near 193 nm is known well as a baseresin of the most general resist for use in ArF. As the above acrylictype resin, since it excels in dry etching resistance, the resin whichhas, as a main chain, the structural unit derived from (α-lower alkyl)acrylic ester [(α-lower alkyl) acrylate] which contains polycyclic andalicyclic saturated hydrocarbon groups such as an adamantane structureas an acid-dissociable, dissolution-inhibiting group at its ester part(side chain part) is generic (for example, see Patent document 1).

[Patent document 1] Japanese Unexamined Patent Application, FirstPublication No. H10-161313 official report

However, there is a problem in that the acrylic type resin containing anacid-dissociable, dissolution-inhibiting group which consists of apolycyclic and alicyclic saturated hydrocarbon group such as the aboveadamantane structure is expensive. Therefore, in the positive typeresist composition using acrylic type resin, cost reduction and dryetching resistance are needed.

Moreover, in the ion implantation process, a positive type resistcomposition which can reduce cost and which excels in barrier propertiesof ions and destructive resistance of the resist pattern is needed.

The present invention is made in order to solve the above subjects, andit is an object of the present invention to realize cost reduction anddry etching resistance in the positive type resist composition usingacrylic type resin. Moreover, it is another object of the presentinvention to improve the barrier properties of ions and the destructiveresistance of a resist pattern in an ion implantation process, whilemaintaining low cost.

DISCLOSURE OF INVENTION

In order to attain the above object, the present invention adopts thefollowing constitution.

The positive type resist composition of the present invention includes aresin component (A) for use in a resist, having an alkali solubilitywhich increases under the action of an acid, an acid generator component(B) which generates an acid upon being exposed, and an organic solventwhich dissolves the resin component (A) and acid generator component(B), wherein the resin component (A) contains a resin component (A1) foruse in a resist having alkali solubility which increases under theaction of an acid having the following structural units (a1), (a2) and(a3):

-   Structural unit (a1): a structural unit derived from (α-lower alkyl)    acrylic ester which contains acid-dissociable,    dissolution-inhibiting groups expressed by the following general    formula (1):    (In formula (1), R represents a hydrogen atom or a lower alkyl    group, R¹¹ represents an acid dissociable, dissolution inhibiting    groups consisting of chain tertiary alkyl groups).-   Structural unit (a2): a structural unit derived from (α-lower alkyl)    acrylic ester which contains lactone-containing monocyclic or    polycyclic groups,-   Structural unit (a3): a structural unit derived from (α-lower alkyl)    acrylic ester which contains polycyclic and alicyclic hydrocarbon    groups which contain polar groups.

Moreover, the positive type resist composition of the present inventionis used for the positive type resist composition for use an in ionimplantation process.

Moreover, the process for forming a resist pattern of the presentinvention includes forming a resist layer on a substrate using saidpositive type resist composition as set forth in above, exposing saidresist layer selectively, and thereafter performing an alkalidevelopment to form a resist pattern.

Moreover, the process for performing an ion implantation of the presentinvention includes forming a resist layer on a substrate using saidpositive type resist composition as set forth in above, exposing saidresist layer selectively, performing an alkali development to form aresist pattern, and thereafter performing an ion implantation whileusing said resist pattern as a mask.

It should be noted that, in the present invention, the wording “(α-loweralkyl) acrylic acid” means one or both of α-lower alkyl acrylic acid andacrylic acid. Moreover, the wording “α-lower alkyl acrylic acid” meansthat which is obtained by substituting the hydrogen atom which is bondedto the α carbon atom of acrylic acid with a lower alkyl group.

The wording “(α-lower alkyl) acrylate” means one or both of α-loweralkyl acrylate and acrylate. Moreover, the wording “α-lower alkylacrylate” means that which is obtained by substituting the hydrogen atomwhich is bonded to the α carbon atom of acrylic ester with a lower alkylgroup.

Moreover, the wording “structural unit” means a monomer unit whichconstitutes a polymer.

Moreover, the wording “the structural unit derived from (α-lower alkyl)acrylate” means a structural unit obtained by cleaving the ethylenicdouble bond of (α-lower alkyl) acrylate.

Moreover, the wording “exposure” involves “irradiation” of an electronray etc.

In accordance with the present invention, cost reduction and dry etchingresistance can be realized in the positive type resist composition usingacrylic type resin.

Moreover, in accordance with the present invention, in the positive typeresist composition using acrylic type resin, it is possible to reducecost and improve the barrier properties of ions and destructiveresistance of a resist pattern in the ion implantation process.

BEST MODE FOR CARRYING OUT THE INVENTION

[Positive Type Resist Composition]

The positive type resist composition of the present invention is apositive type resist composition which is obtained by dissolving a resincomponent (A) for use in a resist of which alkali solubility increasesunder the action of an acid, and an acid generator component (B) whichgenerates an acid upon being exposed in an organic solvent, in which theabove (A) component contains a specific component (A1).

(A) Component

(A1) Component

The (A1) component has structural units (a1), (a2), and (a3).

The structural unit (a1) has alkali-dissociable, dissolution-inhibitinggroups (acid-dissociable, dissolution-inhibiting groups) which make thecomponent (A1) before exposure alkali-insoluble, and increase the alkalisolubility of the component (A1) after exposure under the action of theacid which is generated from the component (B) by dissociating the aboveacid-dissociable, dissolution-inhibiting groups. Thereby, it is possibleto change the whole component (A) from alkali-insoluble to bealkali-soluble.

Structural Unit (a1)

The structural unit (a1) is expressed by the above general formula (1),which is characterized by having an acid-dissociable,dissolution-inhibiting group which consists of a chain tertiary alkylgroup (alkyl group having no cyclic structure and having tertiary carbonatoms). Since such a structural unit (a1) is low cost, reduction of costof a resist composition can be realized by using this.

In general formula (1), R represents a hydrogen atom or a lower alkylgroup, and R may be either. The above lower alkyl group may be eitherlinear or branched, preferably is an alkyl group having 1 to 5 carbonatoms, and more preferably is a methyl group having one carbon atom.

In general formula (1), R¹¹ is a tertiary alkyl group, preferably atertiary alkyl group having 4 to 10 carbon atoms. Specifically,tert-butyl group, tert-amyl group etc. are exemplary, and tert-butylgroup is preferable, in view of reduction of cost.

The percentage of structural unit (a1) preferably ranges from 20 to 60mol %, for example, in component (A1), and more preferably ranges from30 to 50 mol %. By making it within this range, it is possible tosatisfy all of the demand of reduction of cost, improvement of dryetching resistance, ion barrier properties in the ion implantationprocess, and destructive resistance of a resist pattern.

Structural Unit (a2)

The structural unit (a2) is a structural unit derived from (α-loweralkyl) acrylic ester which contains lactone-containing monocyclic orpolycyclic groups. Thereby, dry etching resistance, ion barrierproperties during an ion implantation process, and the destructiveresistance of a resist pattern can be improved. Moreover, theadhesiveness between a resist layer and a substrate is increased and theoccurrence of film peeling etc. is also reduced in a fine resistpattern. Moreover, the hydrophilicity of the whole component (A1)increases, compatibility with a developer increases, and the alkalisolubility in an exposed part improves, thereby contributing toimproving resolution.

As the structural unit (a2), a structural unit in which a monocyclicgroup consisting of a lactone ring, or polycyclic and alicyclichydrocarbon groups having a lactone ring are bonded to the ester sidechain part of (α-lower alkyl) acrylate is exemplary. As for an α-loweralkyl group, it is the same as that of the above.

It should be noted that the wording lactone ring at this time indicatesone ring including a —O—C(O)-structure, and this is counted as the firstring. Therefore, when it has a lactone ring only, it is called amonocyclic group, on the other hand, when it has another ring structurefurther, it is called polycyclic group, regardless of its structure.

And specifically as a monocyclic group, and a polycyclic group, forexample, a monocyclic group obtained by removing one hydrogen atom fromy-butyrolactone, and a polycyclic group obtained by removing onehydrogen atom from a lactone ring containing polycycloalkane, etc. areexemplary.

Specifically as the structural unit (a2), structural units expressed asthe following constitutional formulae (IV) to (VII), for example, arepreferable.

(in formula (IV), R is the same as the above, and m is 0 or 1.)

(in formula (V), R is the same as the above.)

(in formula (VI), R is the same as the above.)

(in formula (VII), R is the same as the above.)

Among these, the structural unit expressed as above general formula(VII) is preferable because it satisfies all of the demands of low costand dry etching resistance, barrier properties of ions in an ionimplantation process, and the destructive resistance of resist patterns.

The structural unit (a2) is preferably contained in an amount rangingfrom 20 to 60 mol %, especially ranging from 20 to 50 mol % to the sumtotal of all of the structural units which constitute component (A1). Bymaking the percent of structural unit (a2) not less than the lowerlimit, dry etching resistance, the ion barrier properties in the ionimplantation process, and the destructive resistance of a resist patterncan be improved. Moreover, quantitative balance with the otherstructural units can be maintained by making the percentage ofstructural unit (a2) not more than the upper limit.

Structural Unit (a3)

The structural unit (a3) is a structural unit derived from an (α-loweralkyl) acrylate which contains polycyclic and alicyclic hydrocarbongroups which contain polar groups. Thereby, dry etching resistance, theion barrier properties in an ion implantation process, and thedestructive resistance of a resist pattern can be improved.

Moreover, the hydrophilicity of the whole component (A1) increases, thecompatibility with a developer increases, and the alkali solubility inan exposed part is improved, thereby contributing to improvingresolution.

As for an α-lower alkyl group, it is the same as in the above.

As polar groups, hydroxyl groups, cyano groups (CN groups), etc. areexemplary, and especially hydroxyl groups or cyano groups arepreferable.

Although polycyclic and alicyclic hydrocarbon groups may be eitherunsaturated or saturated, they are preferably saturated. And the abovepolar group may be bonded to a carbon atom which constitutes thealicyclic hydrocarbon groups.

As a polycyclic and alicyclic hydrocarbon group, groups obtained byremoving one hydrogen atom from bicycloalkane, tricycloalkane,tetracycloalkane, etc. are exemplary. Specifically, groups obtained byremoving one hydrogen atom from polycycloalkanes, such as adamantane,norbornane, isobornane, tricyclodecane, and tetracyclododecane, etc. areexemplary.

As the structural unit (a3), a structural unit expressed as thefollowing general formula (VIII) is exemplary as a preferable one.

(in formula (VIII), R is the same as in the above, X is a polar group,and n is an integer of 1 to 3.)

That is, among this formula, the number of polar groups X is selectedfrom the range of 1 to 3 (the range of the number n), and it ispreferably 1.

Among these, one in which n is 1 and the polar group is bonded to thetertiary carbon of adamantyl group is preferable.

The structural unit (a3) is contained preferably in an amount rangingfrom 10 to 50%, more preferably in an amount ranging from 20 to 40 mol %to the sum total of all of the constitutional units which constitutecomponent (A1). By making the percent of structural unit (a3) not lessthan the lower limit, dry etching resistance, the ion barrier propertiesin the ion implantation process, and the destructive resistance of aresist pattern can be improved, whereas quantitative balance with theother structural units can be maintained by making the percentage ofstructural unit (a3) not more than the upper limit.

The component (A1) may further contain any structural units other thanstructural units (a1), (a2), and (a3).

For example, structural unit (a4) derived from (α-lower alkyl) acrylicester which contains polycyclic and alicyclic hydrocarbon groups otherthan structural units (a2) and (a3) is exemplary. As for an α-loweralkyl group, it is the same as in the above.

Structural Unit (a4)

Here, in structural unit (a4), the wording “other than structural units(a2) and (a3)” means that it does not overlap these, and although thepolycyclic and alicyclic hydrocarbon groups (polycyclic groups) may beeither saturated or unsaturated, it is preferable that they aresaturated. And various polycyclic groups, similar to those of the abovestructural unit (a3), are exemplary.

In particular, at least one group selected from a tricyclodecanyl group,adamantly group, and tetracyclododecanyl group is industrially availableand hence preferable.

Specifically, as the structural unit (a4), those having a structureexpressed as the following formulae (IX) to (XI) are exemplary.

(in formula (IX), R is the same as in the above.)

(in formula (X), R is the same as in the above.)

(in formula (XI), R is the same as in the above.)

The structural unit (a4) is contained in an amount ranging from 1 to 25mol %, preferably ranging from 10 to 20 mol % to the sum total of all ofthe structural units which constitute component (A1).

Although the mass average molecular weight (based on polystyreneequivalent weight average molecular weight determined using GPC) of theresin of component (A1) is not particularly limited, preferably itranges from 5,000 to 30,000, more preferably it ranges from 6,000 to20,000.

Component (A1) is usually a copolymer.

Component (A1) can be obtained by polymerizing monomers from which eachstructural unit is derived according to a well-known radicalpolymerization using a radical polymerization initiator, for example,azobisisobutyronitrile (AIBN) etc.

Component (A1) essentially contains structural units (a1), (a2), and(a3). The sum total of these structural units is preferably not lessthan 80 mol %, more preferably not less than 90 mol % of component (A1).Component (A1) may be used solely, or two or more sorts may be mixed tobe used.

Moreover, it is possible to add arbitrarily to component (A1) one ormore of resins which are used, for example, as a resin for use in theresist compositions for an ArF excimer laser, in an amount within thelimit by which the object of the present invention is attained, in orderto adjust the performance, other than component (A1).

From a point of reduction of cost, the content of component (A1) incomponent (A) is preferably not less than 50 mass %, more preferably notless than 70 mass % (it may be 100 mass %).

As the resin component to be added, for example, that which is obtainedby combining structural unit (a5) derived from (α-lower alkyl) acrylicacid which has acid-dissociable, dissolution-inhibiting groups differentfrom structural unit (a1), with one or more selected from the abovestructural units (a2), (a3), and (a4) can be used. Among them, a resinwhich essentially contains structural units (a5), (a2), and (a3), andcontains structural unit (a4) arbitrarily is preferable.

Structural Unit (a5)

The structural unit (a5) is a structural unit which is derived from(α-lower alkyl) acrylic acid which has acid-dissociable,dissolution-inhibiting groups different from structural unit (a1).

Although that which is used conventionally as the resin for use in achemically amplified resist can be used arbitrarily as thisacid-dissociable, dissolution-inhibiting groups, in particular, anacid-dissociable, dissolution-inhibiting group which contains polycyclicand alicyclic hydrocarbon groups (polycyclic groups) is preferably usedin order to improve dry etching resistance and resolution.

As structural unit (a5), that which is expressed as above generalformula (1) in which R¹¹ is, for example, an acid-dissociable,dissolution-inhibiting group which contains a polycyclic and alicyclichydrocarbon group is preferably used. Although this alicyclichydrocarbon group may be either saturated or unsaturated, it ispreferably saturated.

Polycyclic groups as such can be suitably selected from, for example,among those proposed in the resin component for use in the resistcomposition of an ArF excimer laser. Among them, an adamantyl group,norbornyl group, and tetracyclododecanyl group are industriallypreferable.

More specifically, those expressed as the following general formulae(I), (II) or (III), etc. are exemplary.

(in formula (I), R is the same as in the above, and R¹ represents alower alkyl group.)

(in formula (II), R is the same as in the above, and each of R² and R³is a lower alkyl group independently.)

(in formula (III), R is the same as in the above, and R⁴ represents atertiary alkyl group.)

In the formula, as R¹, a linear or branched lower alkyl group having 1to 5 carbon atoms is preferable, and a methyl group, ethyl group, propylgroup, isopropyl group, n-butyl group, isobutyl group, pentyl group,isopentyl group, neopentyl group, etc. are exemplary. Among them, analkyl group having 2 or more carbon atoms is preferable, and an alkylgroup having 2 to 5 carbon atoms is more preferable. In this case, thereis a tendency that acid dissociability increases compared to the case ofa methyl group. It should be noted that a methyl group and ethyl groupare industrially preferable.

As for the above R² and R³, each is preferably a lower alkyl grouphaving 1 to 5 carbon atoms, independently. Such a group has a tendencythat the acid dissociability becomes higher than that of a2-methyl-2-adamantyl group.

More specifically, each of R² and R³ is preferably a linear or abranched lower alkyl group, independently, similar to the above R¹. Inparticular, both R² and R³ are industrially preferably a methyl group.Specifically, a structural unit derived from 2-(1-adamantyl)-2-propyl(α-lower alkyl) acrylate is exemplary.

The above R⁴ is a tertiary alkyl group having 4 to 10 carbon atoms, andis industrially preferably a tertiary alkyl group such as a tert-butylgroup and tert-amyl group.

Moreover, although a —COOR⁴ group may be bonded to the 3 or 4 positionof the tetracyclododecanyl group shown in the formula, since thesecontain an isomer, it is not possible to identify the bonding position.Moreover, although the carboxyl group residue of an (α-lower alkyl)acrylate structural unit is also bonded to the 8 or 9 position similarlyshown in the formula, the bonding position cannot be identified.

Since it excels in resolution, in the resin (A2) to be mixed, astructural unit (a5) is contained in an amount preferably ranging from20 to 60 mol %, more preferably ranging from 30 to 50 mol % to the sumtotal of all of the structural units of resin (A2).

In resin (A2), the preferable conditions such as blending percentage,mass average molecular weight, etc. of structural units (a2), (a3) and(a4) are the same as in component (A1).

The preferable range of the whole of component (A) is also the same asthat of component (A1).

Component (B)

In the present invention, as component (B), well-known acid generatorswhich are currently used in the conventional chemically amplified resistcomposition can be used, without being limited particularly. Hitherto,as such an acid generator, various ones are known, onium salt type acidgenerators such as an iodonium salt, a sulfonium salt, etc.; oximesulfonate type acid generators; diazomethane type acid generators, suchas bisalkyl or bisaryl sulfonyl diazomethanes, poly(bissulfonyl)diazomethanes, diazomethane nitrobenzyl sulfonates, etc.; iminosulfonatetype acid generators, disulfone type acid generators, etc.

As onium salt type acid generators, specifically,trifluoromethanesulfonate or nonafluorobutanesulfonate ofdiphenyliodonium, trifluoromethanesulfonate or nonafluorobutanesulfonateof bis(4-tert-butylphenyl)iodonium; trifluoromethanesulfonate oftriphenylsulfonium, heptafluoropropanesulfonate thereof ornonafluorobutanesulfonate thereof; trifluoromethanesulfonate oftri(4-methylphenyl)sulfonate, heptafluoropropanesulfonate thereof ornonafluorobutanesulfonate thereof; trifluoromethanesulfonate ofdimethyl(4-hydroxynaphthyl)sulfonium, heptafluoropropanesulfonatethereof or nonafluorobutanesulfonate thereof; trifluoromethanesulfonateof monophenyldimethylsulfonium, heptafluoropropanesulfonate thereof ornonafluorobutanesulfonate thereof; trifluoromethanesulfonate ofdiphenylmonomethylsulfonium, heptafluoropropanesulfonate thereof ornonafluorobutanesulfonate thereof, etc. are exemplary.

As an oximesulfonate type acid generator, specifically, α-(methylsulfonyl oxyimino)-phenyl acetonitrile, α-(methyl sulfonyloxyimino)-p-methoxyphenyl acetonitrile, α-(trifluoromethyl sulfonyloxyimino)-phenyl acetonitrile, α-(trifluoromethyl sulfonyloxyimino)-p-methoxyphenyl acetonitrile, α-(ethyl sulfonyloxyimino)-p-methoxyphenyl acetonitrile, α-(propyl sulfonyloxyimino)-p-methyl phenyl acetonitrile, α-(methyl sulfonyloxyimino)-p-bromophenyl acetonitrile, etc. are exemplary. Among these,α-(methyl sulfonyl oxyimino)-p-methoxyphenyl acetonitrile is preferable.

In diazomethane type acid generators, as bisalkyl or bisaryl sulfonyldiazomethanes, specifically, bis(isopropyl sulfonyl)diazomethane,bis(p-toluene sulfonyl)diazomethane, bis(1,1-dimethyl ethylsulfonyl)diazomethane, bis(cyclohexyl sulfonyl)diazomethane, bis(2,4-dimethylphenyl sulfonyl)diazomethane, etc. are exemplary.

Moreover, as poly(bis sulfonyl)diazomethanes, for example,1,3-bis(phenyl sulfonyl diazomethyl sulfonyl)propane (Compound A,decomposition point 135° C.) having the structure shown below, 1,4-bis(phenyl sulfonyl diazomethyl sulfonyl) butane (Compound B decompositionpoint 147° C.), 1,6-bis(phenyl sulfonyl diazomethyl sulfonyl)hexane(Compound C, melting point 132° C., decomposition point 145° C.),1,10-bis(phenyl sulfonyl diazomethyl sulfonyl)decane (Compound D,decomposition point 147° C.), 1,2-bis(cyclohexyl sulfonyl diazomethylsulfonyl)ethane (Compound E, decomposition point 149° C.), 1,3-bis(cyclohexyl sulfonyl diazomethyl sulfonyl)propane (Compound F,decomposition point 153° C.), 1,6-bis(cyclohexyl sulfonyl diazomethylsulfonyl)hexane (Compound G, melting point 109° C., decomposition point122° C.), and 1,10-bis(cyclohexyl sulfonyl diazomethyl sulfonyl)decane(Compound H, decomposition point 116° C.), etc. are exemplary.

As component (B), one kind of acid generator may be used alone, and twoor more acid generators may used in combination.

The content of component (B) ranges from 0.5 to 30 mass parts,preferably from 1 to 10 mass parts to 100 mass parts of component (A).If the content of component (B) is less than the above range, then thereis a possibility that pattern formation may not sufficiently beperformed, whereas if the content of component (B) is more than theabove range, then there is a possibility that a uniform solution will behard to obtain, such that storage stability may deteriorate.

Nitrogen-Containing Organic Compound (D)

Into the positive type resist composition of the present invention, as afurther arbitrary component, a nitrogen-containing organic compound (D)(referred to as “component (D)” below) may be blended, in order toimprove the resist pattern form and the post exposure stability of thelatent image formed by the pattern-wise exposure of the resist layer.

Since various substances have been already proposed, as component (D),it is possible to select any one from well-known ones and use itarbitrarily, however, amines, in particular secondary lower aliphaticamines, and tertiary lower aliphatic amines are preferable.

Here, the wording “lower aliphatic amine” means an amine of an alkyl oralkyl alcohol having a carbon number of five or less, and as thesecondary amine or the tertiary amine, trimethylamine, diethyl amine,triethyl amine, di-n-propyl amine, tri-n-propyl amine, tri-pentyl amine,diethanol amine, triethanol amine, triisopropanol amine, etc. areexemplarly, however, in particular, a tertiary alkanol amine such astriethanol amine is preferable.

These may be used solely and two or more of them may be used incombination.

Component (D) is usually used in an amount ranging from 0.01 to 5.0 massparts to 100 mass parts of component (A).

Component (E)

Moreover, an organic carboxylic acid, an oxoacid of phosphorus, orderivative thereof (E) (referred to as “component (E)” below) may beadded as a further arbitrary component, in order to preventdeterioration of sensitivity due to addition of the above component (D)and to improve the resist pattern form and the post exposure stabilityof the latent image formed by the pattern-wise exposure of the resistlayer. It should be noted that both components (D) and (E) can be usedtogether, and either component (D) or (E) can be used.

As the organic carboxylic acid, for example, malonic acid, citric acid,malic acid, succinic acid, benzoic acid, salicylic acid, etc. arepreferable.

As the oxoacid of phosphorus or derivatives thereof, phosphoric acid, ora derivative such as phosphoric di-n-butyl ester, and phosphoricdiphenyl ester, etc.; phosphonic acid and derivatives such as phosphonicacid dimethyl ester, phosphonic acid-di-n-butyl ester, phenyl phosphate,phosphonic acid diphenyl ester, phosphonic acid dibenzyl ester, etc.;phosphinic acid and derivatives such as phenyl phosphinate, etc. areexemplary. Among these, phophonic acid is particularly preferable.

Component (E) is used in an amount ranging from 0.01 to 5.0 mass partsper 100 mass parts of component (A).

The Other Arbitrary Components

If necessary, the positive type resist composition of the presentinvention may further contain additives that have compatibility, such asadditional resin for improving the performance of the resist layer, asurface active agent for improving applicability, a dissolutioninhibitor, a plasticizer, a stabilizer, a colorant, an antihalationagent, etc. suitably.

Organic Solvent

The positive type resist composition of the present invention can beproduced by dissolving materials in an organic solvent.

As the organic solvent, any one which can dissolve each component to beused to form a uniform solution can be used. From solvents which areconventionally known well as one for a chemically amplified resist, oneor more can be selected arbitrarily and used.

For example, ketones such as γ-butyrolactone, acetone, methyl ethylketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, etc.;polyhydric alcohols and derivatives thereof, such as ethylene glycol,ethylene glycol monoacetate, diethylene glycol, diethylene glycolmonoacetate, propylene glycol, propylene glycol monoacetate, dipropyleneglycol, or dipropylene glycol monoacetate monomethylether, monoethylether, monopropyl ether, monobutyl ether or monophenyl ether, etc.;cyclic ethers such as dioxane; esters, such as methyl lactate, ethyllactate (EL), methyl acetate, ethyl acetate, butyl acetate, methylpyruvate, ethyl pyruvate, methyl methoxy propionate, ethyl ethoxypropionate, etc. are exemplary.

These organic solvents may be used alone, and may be used as a mixedsolvent containing two or more of them.

In the present invention, it is particularly preferable that the organicsolvent contain ethyl lactate (EL). Thereby a thick resist layer can beeasily produced even if the solid content of the resist composition is acomparatively low concentration of approximately 20 mass % in making aresist layer be a thick film, as mentioned below.

From this point of view, the concentration of EL in the organic solventis preferably over 60 mass %, more preferably over 70 mass %. Althoughthe EL concentration may be 100 mass %, there is a possibility of cracksbeing easily generated in the resist layer, and in that case it ispreferable to add propylene glycol monomethyl ether acetate (PGMEA)thereto further. From a viewpoint of suppressing cracks, the PGMEAconcentration ranges from 5 to 40 mass % in the organic solvent, andpreferably ranges from 10 to 20 mass %.

Although the amount of organic solvent to be used is not particularlylimited, the amount is suitably determined so as to be applicable onto asubstrate, etc., based on the thickness of the coated film. The amountof organic solvent to be used generally ranges from 2 to 20 mass % interms of solid content of the resist composition, and preferably rangesfrom 5 to 15 mass %.

The positive type resist composition of the present invention excels incost, ion barrier properties, and destructive resistance of a resistpattern and hence is suitable as a positive type resist composition foruse in ion implantation.

In particular, if a resist layer (resist pattern) having a thicknessranging from 1.0 to 2.0 μm, preferably ranging from 1.0 to 1.5 μm formedusing the positive type resist composition which contains the abovemixed solvent consisting of EL and PGMEA is used in ion implantationprocess, then no cracks will be generated in the resist layer (resistpattern), and it excels in ion barrier properties, and hence it isparticularly preferable. Therefore, the positive type resist compositionof the present invention is still more suitable for use in ionimplantation to which such a process is applied.

[Process for Forming a Resist Pattern and Etching]

The process for forming a resist pattern of the present invention can beperformed as follows, for example.

That is, at first the above positive type resist composition is appliedby a spinner etc. onto a substrate such as a silicon wafer, thenpre-baking is performed for 40 to 120 seconds, for 60 to 90 seconds at atemperature ranging from 80 to 150° C., and thereafter the resultantsubstrate is subject to selective exposure through a desired maskpattern using an exposing apparatus, and then PEB (Post Exposure Bake)is performed for 40 to 120 seconds, preferably 60 to 90 seconds under atemperature ranging from 80 to 150° C.

Subsequently, the resultant substrate is developed using an alkalideveloper, for example, a 0.1 to 10 mass % aqueous tetra-methyl ammoniumhydroxide solution. Thus, a resist pattern which closely follows a maskpattern can be obtained.

Depending on the case, the above post baking process may be includedafter alkali development, and an antireflection film of an organic typeor an inorganic type may be disposed between the substrate and thecoated layer of the resist composition. The post baking is performed,for example, under the conditions of a temperature ranging from 90 to150° C. and a period ranging from 30 to 90 seconds.

Subsequently, the substrate under the resist pattern is etched using theresist pattern as a mask. The etching method may be either a wet etchingmethod, or dry etching method. In the case of wet etching, the etchingis performed while immersing the substrate in an aqueous fluoric acid(hydrofluoric acid) solution having a concentration of approximately 20mass % for 3 minutes, for example. In the case of dry etching, theetching is performed using halogen type gas such as tetrafluoromethane,trifluoromethane, etc.; helium gas, oxygen gas, etc., for example.

The positive type resist composition of the present invention is lowcost, and excellent in dry etching resistance. Furthermore, the effectthat the resist pattern after wet etching is hardly peeled is alsoobtained. Therefore, either dry etching, which is frequently usedrecently because of its high processing accuracy, or wet etching can beused, and hence the degree of freedom is high.

Moreover, the wavelength of light to be used for exposing is not limitedparticularly, and the exposing can be performed using ultravioletradiation such as i line, g line, h line, etc., and radioactive rayssuch ArF excimer laser, KrF excimer laser, F₂ excimer laser, EUV(extreme ultraviolet rays), VUV (vacuum ultraviolet radiation) and EB(electron beam), X-rays, and soft X rays, etc.

The positive type resist composition in accordance with the presentinvention is particularly suitable for forming a thick resist layer byusing an exposing apparatus for i lines, an exposing apparatus for a KrFexcimer laser, and an exposing apparatus for ArF excimer laser. It ispreferable to use an exposing apparatus for i line and an exposingapparatus for a KrF excimer laser from the viewpoint of cost reduction.From the point of view of fine processing, an exposing apparatus for anArF excimer laser is preferable.

A thick resist layer means that the thickness after pre-baking rangesfrom 0.6 to 2.0 μm, preferably from 1.0 to 1.5 μm, for example.

[Process for Performing Ion Implantation]

The process for performing ion implantation of the present invention isa process which includes forming a resist layer onto a substrate usingthe positive type resist composition of the present invention, exposingselectively onto the resist layer, performing alkali development to forma resist pattern, and thereafter performing ion implantation using theresist pattern as a mask.

An ion implantation per se is well-known, which ionizes the targetsubstance, and accelerates ions electrostatically, thereby implantingions into a solid (thin film on a substrate).

As ion acceleration energy at the time of this ion implantation, anenergy load ranging from 10 to 200 keV is applied to a resist pattern,and the resist pattern may be destroyed. As an ion source, ions, such asboron, phosphorus, arsenic, argon, etc. are exemplary. As a thin film onthe substrate, silicon, silicon dioxide, silicon nitride, aluminum, etc.are exemplary.

In the process of the present invention, the above positive type resistcomposition may be used in such a process for performing ionimplantation.

Since component (A1) has high transparency of, for example, not lessthan 0.11/gm of gram absorption coefficient to light having a wavelengthof 193 nm [measuring method: well-known method which includes applying asolution of component (A1) onto a quartz glass substrate, drying it at120° C. for 60 seconds to form a film having a thickness of 1.0 μm, andmeasuring this film by a spectrophotometer at a wavelength of 193 nm.],it can be used for a thick film having a thickness ranging from 0.6 to2.0 μm, preferably from 1.0 to 1.5 μm.

Moreover, when forming a thick resist layer, it is possible to decreasethe influence of standing waves due to reflection of exposed light,etc., even without forming an antireflection film, thereby providing aneffect that deterioration of form of patterns such as standing waves,etc. hardly occur. This effect is effective especially in the processfor performing ion implantation which does not necessitate anantireflection film.

In accordance with the present invention, since the structural unit (a1)which has the acid-dissociable, dissolution-inhibiting groups whichconsist of the chain tertiary alkyl group can be used, significant costreduction can be obtained. Moreover, the dry etching resistance, the ionbarrier properties during the ion implantation process, and thedestructive resistance of a resist pattern which are required, are alsosatisfied.

Here, an acrylic type resin which has acid-dissociable,dissolution-inhibiting groups consisting of the chain tertiary alkylgroup like structural unit (a1) was conventionally considered to beremarkably inferior in dry etching resistance, and hence it was notused. For example, in Patent document 1, in paragraph [0029], it isdisclosed that even if a substance has acid-dissociable,dissolution-inhibiting groups which contain monocyclic and alicyclicgroups, the substance is insufficient in dry etching resistance, and itis suggested that if a substance is a chain tertiary alkyl group, thenit will be further inferior in the dry etching resistance. Therefore,based on conventional technical common sense, structural unit (a1)cannot have been adopted from the viewpoint of “dry etching resistance”,which is an object of the present invention.

On the other hand, the inventors of the present invention have foundthat the required dry etching resistance, the ion barrier propertiesduring the ion implantation process, and the destructive resistance of aresist pattern can be obtained by combining structural units (a1), (a2)and (a3) suitably, even if structural unit (a1) is introduced, and as aresult they have completed the present invention, which realizes bothreduction of cost and improvement of dry etching resistance at the sametime.

Moreover, the objects of reduction of cost, improvement of the ionbarrier properties during ion implantation and the destructiveresistance of a resist pattern have also been attained.

In accordance with the present invention, the effect of excelling in wetetching ability (characteristic in that the interface between the resistlayer and the substrate is hardly peeled) is also further obtainable.

Moreover, in accordance with the present invention, resolution is alsocomparatively excellent.

EXAMPLES Synthetic Example 1 Polymer 1

A resin component (polymer 1) which consists of 40 mol % of thefollowing structural unit (a1), 40 mol % of structural unit (a2) and 20mol % of structural unit (a3) was synthesized. The mass averagemolecular weight of the polymer 1 was 8660, and the degree of dispersion(mass average molecular weight/number average molecular weight) was1.78.

-   Structural unit (a1): The structural unit in which R=methyl group    and R¹¹=tert-butyl in the above general formula (1).-   Structural unit (a2): The structural unit in which R=methyl group in    the above general formula (VII).-   Structural unit (a3): The structural unit bonded to the tertiary    position of an adamantyl group, in which R=methyl group, n=1, and X    is a hydroxyl group in the above general formula (VIII).

Synthetic Example 2 Polymer 2

A resin component (polymer 2) which consists of 40 mol % of thefollowing structural unit (a1), 40 mol % of structural unit (a2) and 20mol % of structural unit (a3) was synthesized. The mass averagemolecular weight of polymer 2 was 9000, and the degree of dispersion(mass average molecular weight/number average molecular weight) was1.78.

-   Structural unit (a1): The structural unit in which R=methyl group    and R¹¹=tert-butyl in the above general formula (1)-   Structural unit (a2): The structural unit in which is R=methyl group    in the above general formula (VII).-   Structural unit (a3): The structural unit bonded to the tertiary    position of an adamantyl group, in which R=methyl group, n=1, and X    is a CN group, in the above general formula (VIII).

Comparative Synthesis Example 1 Polymer 3

A resin component (polymer 3) which consists of 40 mol % of thefollowing structural unit (a5), 40 mol % of structural unit (a2) and 20mol % of structural unit (a3) was synthesized. The mass averagemolecular weight of the polymer 3 was 13000, and the degree ofdispersion (mass average molecular weight/number average molecularweight) was 1.93.

-   Structural unit (a5): The structural unit derived from 2-methyl    adamantyl methacrylate in which R=methyl group and R¹ is a methyl    group in the above general formula (I).-   Structural unit (a2): The structural unit in which R=methyl group in    the above general formula (VII).-   Structural unit (a3): The structural unit in which R=methyl group,    n=1, and X is a hydroxyl group, in the above general formula (VIII),    and has been bonded to the tertiary position of an adamantyl group.

Example 1

Above polymer 1 [which corresponds to component (A1)] as component (A)and the following material were dissolved in an organic solvent and thepositive type resist composition was produced.

-   Component (A): 100 mass parts-   Component (B): 2 mass parts of a triphenyl sulfonium    nonafloorobutanesulfonate to 100 mass parts of component (A).-   Organic solvent: Mixed solvent of EL/PGMEA=9/1 (mass ratio), 408    mass parts (20% concentration of solid content as a resist solution)    to 100 mass parts of component (A).-   Component (D): triethanol amine, 0.1 mass parts to 100 mass parts of    component (A).

Example 2

A positive type resist composition was produced by the same way as inExample 1 with the exception of using the above polymer 2 [whichcorresponds to component (A1)] as component (A).

Comparative Example

A positive type resist composition was produced by the same way as inExample 1 with the exception of using the above polymer 3 as component(A). It should be noted that since the above polymer uses the structuralunit derived from 2-methyl adamantyl methacrylate, the object of thereduction in cost is not attained.

(Evaluation Method and Result) (Test Method 1) Peeling by Wet Etching 1.

Onto a silicon substrate 1 (which had been subjected tohexamethyldisilazane treatment under the conditions of a temperature of90° C. for 35 seconds) on which an oxide film (SiO₂) was coated, apositive type resist composition was applied using a spinner, andpre-baking was performed on a hot plate at a temperature of 120° C. for60 seconds to form a resist layer of 1.3 μm after pre-baking.Thereafter, using an ArF exposing apparatus, NSR-S302 (product name,produced by NIKON Co. Ltd.; NA (numerical aperture)=0.6, ⅔-annularillumination), an ArF excimer laser (193 nm) was selectively exposedthrough a mask pattern.

And PEB treatment was performed at 130° C. for 60 seconds, and thendevelopment was performed for 45 seconds using an aqueous 2.38 mass %tetra-methyl ammonium hydroxide solution at 23° C. It should be notedthat, an LD nozzle of a scanning type was used at this time.

Thus, after a pattern of 300 μm in size was formed, post-baking wasperformed at 100° C. for 60 seconds, and then the resultant sample wasimmersed in an aqueous fluoric acid (hydrofluoric acid) solution havinga concentration of approximately 20 mass % for 3 minutes to perform wetetching, and thereafter, the resultant sample was observed with respectto peeling of the pattern through an electron microscope.

(Test Method 2) Peeling by Wet Etching 2

Evaluation was performed by the same way as in the test method 1, withthe exception of using a silicon substrate 2 on which an oxide film wasformed by performing hexamethyldisilazane treatment under the conditionsof 150° C. for 35 seconds.

Results

In Comparative Example, the pattern had been removed completely.

In Examples 1 and 2, in the interface between the substrate and thepattern, slit-like side-etching was generated on the edge of thepattern, however, the pattern per se was remained. Size of theside-etching (the length from the edge of the pattern to the slittip-end of the slit generated on the side cross-section of the patterns)was as follows, which was slight.

-   Example 1: Substrate 1, 1.97 μm; Substrate 2, 1.29 μm-   Example 2: board 1, 2.47 μm; Substrate 2, 2.17 μm    2) Resolution and Observation of the Form

Exposure was performed at the optimal conditions such that a patternhaving 0.5 82 m of line & space was formed at 1:1, using substrate 1. Asa result, all of the positive type resist composition of Examples 1 and2 and Comparative Example was sufficiently resolved to the 0.5 μm ofline & space, and no pattern collapses were generated.

Moreover, each pattern form was rectangular and there was no influenceof standing waves.

3) Evaluation Method of Dry Etching Resistance and Results

As to resist compositions of Examples 1 and 2, resist patterns having aline width of 0.5 μm were formed, the using substrate 1, and then dryetching was performed under the following conditions using an etchingapparatus produced by TOKYO OHKA KOGYO Co., Ltd.

Moreover, here for comparison, a resist composition for use in a generalKrF excimer laser which contains a resin having polyhydroxyl groups ofwhich hydroxyl grous are partially protected with acid-dissociable,dissolution-inhibiting groups was used.

Conditions:

Type and flow rate of the etching gas: Mixed gas of tetrafluoromethane30 cc/min., trifluoromethane 30 cc/min., and helium 100 cc/min.

-   Pressure: 300 mmTorr-   Output power: 600 W-   Time: 120 seconds

As a result, the resist patterns formed using the resist compositions ofExamples 1 and 2 had a remaining amount of resist film of 90% andexhibited considerably good dry etching resistance, compared to the KrFresist having the base resin having polyhydroxy styrene of which thehydroxyl groups are partially protected with acid-dissociable,dissolution-inhibiting groups.

4) Evaluation Method of Ion Barrier Properties and Results

As to the resist compositions of Examples 1 and 2 i.e., the same methodas in those described in the peeling by wet-etching 1 up to pre-bakingwas performed to obtain a resist layer having a thickness of 1.3 μm. Ionbarrier properties were evaluated in these layers through a well-knownion implanting apparatus, and it revealed that the ion barrierproperties were satisfactory. Moreover, as ion accelerating energy atthe time of ion implantation, although an energy load ranging from 10 to200 keV was applied to the resist pattern, the resist pattern was notdestroyed. Moreover, although the formed resist pattern did not form anantireflection film, it had an excellent pattern form having no standingwaves.

Thus, in accordance with the resist compositions of Examples 1 and 2 ofthe present invention, they excel in dry etching resistance, ion barrierproperties during ion implantation, and destructive resistance.Therefore, it turned out that both cost reduction and dry etchingresistance are possible. Moreover, it turned out that all of costreduction, ion barrier properties, and destructive resistance can beattained simultaneously. The resolution was also practicallysatisfactory. Furthermore, the wet etching property was excellent.

INDUSTRIAL APPLICABILITY

The present invention provides a positive type resist composition usingan acryl type resin used for producing a semiconductor device or aliquid crystal display device, which excels in cost reduction, ionbarrier properties in an ion implantation process and destructiveresistance of a resist pattern, and is very useful in industry.

1. A positive type resist composition comprising a resin component (A)for use in a resist, having alkali solubility which increases under theaction of an acid, an acid generator component (B) which generates anacid upon being exposed, and an organic solvent which dissolves theresin component (A) and the acid generator component (B), wherein theresin component (A) contains a resin component (A1) for use in a resisthaving alkali solubility which increases under the action of an acidhaving the following structural units (a1), (a2) and (a3): structuralunit (a1): a structural unit derived from an (α-lower alkyl) acrylicester which contains acid-dissociable, dissolution-inhibiting groupsexpressed by the following general formula (1):

(in formula (1), R represents a hydrogen atom or a lower alkyl group,R¹¹ represents acid-dissociable, dissolution-inhibiting groupsconsisting of chain tertiary alkyl groups), structural unit (a2): astructural unit derived from an (α-lower alkyl) acrylic ester whichcontains lactone-containing monocyclic or polycyclic groups, Structuralunit (a3): a structural unit derived from an (α-lower alkyl) acrylicester which contains polycyclic and alicyclic hydrocarbon groups whichcontain polar groups.
 2. The positive type resist composition as setforth in claim 1, wherein said acid-dissociable, dissolution-inhibitinggroups in said structural unit (a1) are tert-butyl groups.
 3. Thepositive type resist composition as set forth in claim 1 wherein saidstructural unit (a2) is a structural unit expressed as the followinggeneral formula.

(in the formula, R represents a hydrogen atom or a lower alkyl group) 4.The positive type resist composition as set forth in claim 1, whereinsaid structural unit (a3) is a structural unit expressed as thefollowing general formula.

(in the formula, R represents a hydrogen atom or a lower alkyl group, Xrepresents a polar group, and n represents an integer of 1 to 3.)
 5. Thepositive type resist composition as set forth in claim 1, wherein saidorganic solvent contains ethyl lactate (EL).
 6. The positive type resistcomposition as set forth in claim 5, wherein said organic solventfurther contains propylene glycol monomethyl ether acetate (PGMEA). 7.The positive type resist composition as set forth in claim 1, furthercomprising a nitrogen-containing organic compound.
 8. A positive typeresist composition for use in ion implantation as set forth in claim 1.9. A process for forming a resist pattern, comprising: forming a resistlayer on a substrate using said positive type resist composition as setforth in claim 1, exposing selectively onto said resist layer, andthereafter performing alkali development to form a resist pattern.
 10. Aprocess for performing an ion implantation, comprising: forming a resistlayer on a substrate using said positive type resist composition as setforth in claim 1, exposing selectively onto said resist layer,performing alkali development to form a resist pattern, and thereafterperforming ion implantation while using said resist pattern as a mask.